1. Field of the Invention
The present invention relates to a concept for making goal decisions by means of magnetic fields as may be employed, for example, in football for making goal decisions.
2. Description of Prior Art
For quite some time, various interest groups have wished to study and understand the sequence of movements of moving objects and/or persons, which requires an exact indication of the object's position in space and time. What is of particular interest here are, among other things, game balls, in particular in commercialized types of sport, such as footballs, or soccer balls, which are highly accelerated in three-dimensional space, as well as tennis or golf balls. The question of who was the last to touch the object of the game, how it was hit and whether it crossed a goal line further may be decisive for the outcome of the game, depending on the type of game.
Game devices that are used in high-performance sports, such as tennis balls, golf balls, footballs and the like, nowadays can be accelerated to extremely high speeds, so that the detection of the object during the movement requires highly sophisticated technology. The technical means employed so far—mainly cameras—either completely fail to meet the requirements set forth above, or meet them only to an insufficient degree; also the methods, hitherto known, for position finding by means of various transmitter and receiver combinations still leave a large error margin with regard to the spatial resolution of the position indication, with regard to the ease of use of the transmitter/receiver components required, and above all with regard to evaluating the data obtained by means of the transmitter/receiver system, so that it is not yet possible, or at least requires a large amount of effort, to evaluate the results obtained from this data as fast as possible.
It is not only in the field of commercial sports, where movable game devices may be employed, but it is also in the personal field that users have become more and more used to electronic devices indicating various pieces of information to give a user feedback as to how he/she has affected an object, or to provide him/her with information about where a game device is currently situated, for example.
A multiplicity of tasks, such as making goal decisions in a football match, presuppose knowledge of the position and/or orientation of a movable object, such as a ball. In football matches, the question of whether or not the ball has exceeded the goal line is, in critical situations, one of the most controversial topics. To this end, it is necessary that the position of the ball can be measured at the goal line within an accuracy range of about +/−1.5 cm. In addition, any influence exerted by persons who are moving close to the ball and/or cover the ball, must not play any part in this.
There are numerous methods by means of which a referee's goal decision may be reconstructed. These methods are based, for example, on two-dimensional or three-dimensional optical sensors having an evaluation system, on exploiting the known radar principle, or on a principle of radio localization. Evaluating video recordings, for example with goal cameras, generally requires a lot of effort, and a two-dimensionality of the image plane systems often yields distorted values.
With the principle of radio localization, a movable object, or the ball, is localized by means of electromagnetic wave propagation. For example, a receiver and/or transmitter is integrated into or attached to the ball which, upon request, may send data to a central transmitting/receiving device. The position of the ball may then be calculated, for example, from signal delay times and/or from differences between signals received at at least two different antennas. A disadvantage of radio localization consists, for example, in a shadowing and/or in a reflection of electromagnetic waves by certain obstacles, such as persons. For this reason, systems which are based on radio localization do not achieve the level of accuracy required for making a goal decision in football.
As has already been described, current localization methods are based, for example, on optical sensors having an evaluation system (video evaluation system), or they are based on the use of RF transponders within and outside the movable object, or the ball. Such localization methods for making goal decisions entail high investment and maintenance cost, sensitivity toward environmental conditions and a large outlay in terms of adapting the evaluation algorithms. For close-range localization, i.e. position determination regarding an object within a small area, systems using radio localization are not suitable, since with a small geometrical expansion, differences of various signal delay times are hardly measurable any more. Thus, the requirements placed upon systems for localizing a movable object are not met, or are met only to an insufficient degree, by this method with regard to economy, robustness, clock time and object independence, for accurate position determination for making goal decisions, for example within a range of a few centimeters.